Study on Cytotoxicity and Nucleotide Sequences of Enterotoxin FM of Bacillus cereus Isolated from Various Food Sources
Nudjaree Boonchai MSc*, Shin-Ishiro Asano PhD**, Hisanori Bando PhD**, Chanpen Wiwat PhD*
Affiliation : * Department of Microbiology, Faculty of Pharmacy, Mahidol University, Bangkok, Thailand ** Faculty of Agriculture, Hokkaido University, Sapporo, Hokkaido, Japan
Objective : To determine the cytotoxicity of the crude culture broth containing enterotoxins of B. cereus and
investigate the nucleotide sequences of ent FM among various isolates B. cereus.
Material and Method: The 1.2 kb fragment of ent FM of B. cereus was amplified, cloned, sequenced, and
compared with published sequences. The biological activity of crude culture broth containing enterotoxins
with and without monoclonal antibodies against HBL, NHE, and EntFM enterotoxins was tested using Vero
cells assay.
Results : A percentage homology of nucleotide sequences and deduced amino acid sequences among test
isolates and published strains were 90-99% and 88-99%, respectively. An assays for cytotoxic activity
revealed that seven and three of B. cereus isolates were positive for NHE enterotoxin and EntFM enterotoxin,
respectively. In addition, the 4-repeating sequences “TCAAAC” of ent FM were found, which may or may not
be probably correlated with cytotoxicity of B. cereus.
Conclusion : The enterotoxin FM from B. cereus isolates is cytotoxic and the degree of cytotoxicity depends on
the bacterial strain.
Keywords : Bacillus cereus, Enterotoxin FM, Food poisoning, Cytotoxicity, Sequencing
